The present invention concerns a rotating bezel particularly for a timepiece such as a wristwatch, a clock or an alarm clock with a mechanical or electronic movement. This rotating bezel can be termed xe2x80x9cmysteriousxe2x80x9d in that the orientation of the indications carried by the bezel, such as alphanumerical signs, always remain the same, i.e. these indications are always legible in the same direction as the indications marked on the dial whatever the rotational angle imparted to the bezel.
In all the currently known wristwatches with a rotating bezel, for example diving watches, the indications are marked on the bezel in radial directions such that it is possible to read them properly only when an indication is brought to the 12 o""clock position, with the obvious risk of the figures 6 and 9 being confused at the moment of selection. A watch of this type, with the figures from 1 to 12 being the indications carried by the bezel, is shown in FIG. 1.
However, there exists a Japanese Patent No. JP 2599334, which attempts to provide a solution to the aforementioned problem. In the proposed device, the principle of which is shown in FIG. 2, the indications are carried by studs that are rotationally mobile in housings of the bezel, each stud having at its base a stem that is offset with respect to the axis of the stud. The stem is engaged in a circular groove of the same diameter as the circle described by the rotational axis of the studs, but whose centre is offset with respect to the centre of the dial by a distance equal to the distance between the rotational axis of each stud and the stem. For a rotation less than 180xc2x0, the indications maintain a vertical reading position. The 180xc2x0 position (at 6 o""clock here) corresponds to an unstable position in which either a blockage can occur, which was observed by the inventors of the present invention, or rotation can continue beyond 180 xc2x0 still maintaining the vertical position, but also with the risk of creating a tipping movement causing the stems of two successive studs to come closer together as shown in FIG. 2, a the 5 o""clock position. In order to overcome this drawback, the author proposes placing a washer at the base of the studs, through which the stems of the studs pass at regular intervals, said washer being driven in rotation at the same time as the bezel. This solution, which requires the use of an additional part, theoretically allows the desired object to be attained but, because of the contact surface of the washer on the edges of the groove, has the major drawback of considerably increasing friction, to such a point that no product known to the Applicant includes such a device.
The present invention provides a different solution, allowing the drawbacks of the aforecited prior art to be overcome by providing a rotating bezel having a reduced number of parts to be assembled, and allowing the bezel to rotate freely, while still keeping the indications borne by the latter legible in the same direction.
The invention therefore concerns a rotating bezel comprising a ring able to rotate freely on a base in order to bring a selected indication opposite a determined mark of the base or a dial located at the centre of the bezel. The indications, alphanumerical characters, pictograms or other elements, are not directly marked on the ring but on the outer surface of studs that are each able to rotate freely about their axis of revolution in a housing arranged through the thickness of the ring and opening onto the base. Each stud includes on its lower part at least two stems of different dimensions, offset by the same distance from the axis of revolution of the studs, and having an angular offset less than 180xc2x0. When the bezel is driven in rotation, each stem is guided by a circular groove formed in the base and having a cross-section adapted to the dimensions of each stem, a radius equal to that of-the circle described by the axis of revolution of the studs, the centres of each groove having, with respect to the centre of the dial, exactly the same arrangement as the stems with respect to the axis of revolution of the studs.
When the studs include only two stems, the stems must not be aligned on the same diameter, otherwise there would still be the risk, as in the aforecited prior art, of an unstable position in which the rotation of the bezel could be blocked, or beyond which a reversion of the rotational direction of the studs in their housing could occur. With the proposed construction, the grooves necessarily intersect and, in a way, create switches. According to the invention, in order for each stem to recognise the direction to take in a switch, the stems of each stud and correlatively the cross-sections of the grooves, have different dimensions, either in length, or in diameter, or both in length and diameter. Although each stud can only include two stems, tests have shown that the most satisfactory result is obtained with studs including three studs offset angularly by 120xc2x0 and differentiated both by their length and their diameter.